src code

class method Object.keys 

Object.keys(object) → Array
  • object (Object) – The object to pull keys from.

Returns an array of the object's property names.

Note that the order of the resulting array is browser-dependent — it relies on the for...in loop, for which the ECMAScript spec does not prescribe an enumeration order. Sort the resulting array if you wish to normalize the order of the object keys.

Examples
Object.keys();
// -> []
 Object.keys({ name: 'Prototype', version: '1.6.1' }).sort();
// -> ['name', 'version']